The overall objective of this research is the elucidation of the molecular mechanisms involved in the induction of tumors by chemical carcinogens. This objective is being approached through the characterization of the proximate and ultimate carcinogenic metabolites of administered carcinogens and by an analysis of the reactions of ultimate carcinogenic metabolites with tissue constituents. A basic concept which underlies the study is the finding that the ultimate carcinogenic derivatives of chemical carcinogens are in most, if not all, cases strong electrophilic reactants. This concept is being used as a guide in studies on various carcinogenic amines and amides, safrole and related benzylic and allylic derivatives, aflatoxin B1, and the diphenyl acetylenic carbamates.